On Sat, Sep 24, 2016 at 9:07 AM, Peter Geoghegan <p...@heroku.com> wrote: > On Thu, Sep 22, 2016 at 8:57 PM, Robert Haas <robertmh...@gmail.com> wrote: >> On Thu, Sep 22, 2016 at 3:51 PM, Heikki Linnakangas <hlinn...@iki.fi> wrote: >>> It'd be good if you could overlap the final merges in the workers with the >>> merge in the leader. ISTM it would be quite straightforward to replace the >>> final tape of each worker with a shared memory queue, so that the leader >>> could start merging and returning tuples as soon as it gets the first tuple >>> from each worker. Instead of having to wait for all the workers to complete >>> first. >> >> If you do that, make sure to have the leader read multiple tuples at a >> time from each worker whenever possible. It makes a huge difference >> to performance. See bc7fcab5e36b9597857fa7e3fa6d9ba54aaea167. > > That requires some kind of mutual exclusion mechanism, like an LWLock.
No, it doesn't. Shared memory queues are single-reader, single-writer. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers